Various kinds of printers electrophotographic printers ink jet printers thermal printers etc. have been commercialized especially for DTP. The authors however have been unsatisfied with the image-quality of these printers. A laser recording apparatus was made for our study which is composed of a laser diode a polygonal mirror and a F-theta optical system. The recording apparatus selectively provides high density pixel (600 900 or 1 200 dpi). The gradation of each pixel is obtained by modulating the pulse width of the laser diode oscillation. We used the silver halide paper (PD-100WP Fuji Photo Film Co. Ltd. ) with the good spectrum sensitivity for the laser diode of 780 nm wavelength. The recorded image samples with three kinds of pixel densities and with gradation levels ranging from 16 to 166 were used for being evaluated by sixteen persons. As a result of analysis on the evaluated data we found out some relations between pixel densities and gradation levels for the satisfactory image-quality. 2.

The visibility of the modulatorinduced streaking artifact in the images from a laser film printer has been observed and analyzed. These streaks which occur in the printing of a light (low density) area after the printing of a dark (high density) area can be ascribed to the reflection of acoustic power in the acoustooptic modulator. By comparing the fractional transmission change in the light area (due to the reflection of acoustic power used for the printing of the dark area) with a visual threshold contrast the visibility of streaks can be determined. These results are found to be in good agreement with experiments. Specifications on the maximum acoustic reflection coefficient for the suppression of streaking visibility are also given. 1.

A laser scanning optics module for use with a compact laser printer has been developed. This optics module features an f-theta concave mirror made from precision molded plastic rather than polished glass and which gives 300 dots per inch resolution. Compared with Minolta's previous compact laser printer, the size of the module has been reduced by forty percent and the production costs of the module have been halved. The reduction in size is achieved both by providing a forty percent wider scanning angle than that used previously and by using the concave f-theta mirror to reflect the scanning beam back in the direction from which it came. The production costs have been reduced by replacing the three glass lenses used in the previous module with two molded plastic elements of a single concave f- theta mirror and a single toroidal lens. It was calculated by using simulation software, and subsequently verified in practice, that even when submitted to a temperature increase of forty degrees centigrade from the normal, the performance of this optics module is ensured. Because of the different rates of expansion between the module and the optical elements themselves as the temperature increases, plate springs are used to hold the elements in place, thus eliminating any strain on the optical surfaces. During the test, the spot diameters and the scanning line position of the optics were found to have the same degree of variation as the glass elements which had previously used.

In order to realize high-resolution and compact optical scanning system with simple lens construction , we introduced a simple fO lens construction which corrects higher-order field curvature. And , we also designed an optical scanning system with wave optics , by using developed simulation program which evaluates intensity distribution including the effects of beam truncation. As a result, we developed an optical scanning system which has small spot size (applicable for more than 600 dpi) , and wide scan angle with very simple construction.

Except some special cases the color printing is usually performed by overprinting a series of four plates in yellow (Y) magenta (M) cyan (C) and black (BK) ink. Process Color Scanner is the device that reads the fullcolor on ginal to be reproduced it into four color components (Y and BK) converts the totalvalue into the dot sizes provides the output on the photosensitive materials such as monochrome film on monochrome paper. The optical dot formation of our Process Colon Scanner SG series is performed as follows: 1. Ten light spots that may be independently switched (ON and OFF) at high speed are formed in line on a photosensitive material. 2. Such photosensitive material wrapped around the surface of a notating drum forms the dots on its surface according to the light spots switched by the signals from the dot generator as the drum notates. (See Fig. 1) Conventionally the gas laser (HeNe on Ar) has been used as the light source where a beam from a single laser tube is splitted into ten beams by the use of a beam splitter and an external modulator is provided to each laser beam to control its switching. As the semiconductor laser has the features such as high speed self-modulability and compact size we have developed new exposure system with ten semi conductor laser elements to replace conventional system consisting of a gas a beam splitter and ten external modulators. (See Fig. 2) 1. CONSTRUCTION OF THE SYSTEM 1. 1. Light emitting section The semiconductor laser emitting the light of 780 nm wave length is employed for the matching with photosensitive materials currently available. And as this type of semiconductor laser is also used in compact disc system etc. it offers stable performance and good availability. 1. 2. Method to control the beam Unlike the gas laser beam with an excellent directivity the semi- 68 / SPIE Vol. 1254 Optical Hard Copy and Printing Systems (1990)

The FUJIX SCANART 450 is a monochrome film making scanner developed by FUJI fully utilizing its advanced scanner concepts. Salient features ofthis scanner include the following: 1) Large-sized originals (up to A2 format) can be processed at a high speed of4.5 mm/sec, thus providing enhanced productivity. 2) The scanner meets the highest level ofimage quality demanded in the field ofgraphic arts. 3) To allow for future system expansion, the input scanner has been separated from the output recorder. It is well known that a high level of image quality is required in graphic arts applications, with particular importance being attached to tone reproduction and sharpness in this field. It is also imperative to rule out the possibility ofany noticeable streak or non-uniformity in images. To meet these requirements, we have developed an input scanner employing CCD line sensors and an output recorder based on the laser diode, fully utilizing our accumulated know-how in the field of high-quality image processing technology. This paper discusses the technologies that have been established to take advantage of the features of the CCD. Chiefly among these are firstly, a technology to accommodate originals of large size, to provide the capability to read originals of A2 width (452 mm) with high resolutions; and secondly, a technology to achieve high imagee quality through the implementation of high accuracy compensation for CCD signals.

The first report discussed the specifications and system composition of the input scanner. This paper is concerned primarily with the output recorder.
The output recorder has been designed with two main aims in terms of quality:
1) To achieve sharpness for excellent dot quality; and
2) To eliminate streaks and shading for superior image quality.
This paper discusses (1) laser diode (LD) optical processing technology, (2) resonant scanner (RS) mirror shape design technoloqy, and (3) LD high-speed drive technology, all of which are closely related to the quality targets mentioned above.

A full size 400 dpi Edge Emitter array was designed and constructed. The light-emitting edge is 8. 18 inches long capable of printing across the full width of the page. An Edge Emitter head was assembled consisting of three components: a 400 dpi Edge Emitter array a circuit board containing the channel driver ICs and a SELFOC R lens array in a frame. The frame also provided the means of mounting in a 6 ppm electrophotographic printer. Pages of graphics and alphanumerics were printed to demonstrate capabilities of the Edge Emitter array. 1.

An experimental high resolution cathode ray tube (CRT) printer was developed to produce high quality 3. 5in. x 5 in. and 4 in. x 6 in. photographic prints. A monochrome CRT utilizing red green and blue filtration was used to sequenlially expose continuous-tone color images directly onto conventional photographic paper. A summary of the design and implementation of the printer at the systems level will be presented. The design approach taken to meet the system quality requirements is described from the electrical mechanical and optical points of view. In addition the presentation will emphasize the design challenges of implementing a CRT imager and the solutions to the unique problems it presents. Other concerns discussed in detail include spatial resolution and bit resolution image size and magnification colorimetry and paper response matching. Sample prints of test patterns and scanned images will be shown. 1.

An experimental high-resolution digital printer has been developed that is capable of directly exposing standard color photographic paper in any of four formats ranging in size from 8 in. by 12 in. to 20 in. by 30 in. The printer utilizes three visible wavelength gas lasers to expose continuous-tone color prints in 60 seconds. Each image contains 4000 pixels by 6000 lines of 8-bit red green and blue data at corresponding pixel pitches of 500 to 200 pixels per inch. Integral optical power measurement standards maintain consistent calibration. The ability to produce artifact-free continuous-tone images over this large area requires a critical design approach in all areas of optical mechanical and electronic design. A systems level discussion will illustrate the approaches taken to meet these design challenges. The printer hardware and calibration systems will be described and their performance will be presented. Sample prints of both internally generated test patterns and image scenes will be shown at the conference but could not be suitably reproduced for these proceedings. 1.

A continuous tone colour film recorder was constructed that exposes 8 x 10 inch ISO 100 daylight-balanced sheet film in ten minutes at a resolution of 1000 pixels/inch. A rotating drum is used for line scan and a leadscrew driven by a stepper motor for page scan. Film loading and unloading is automatic. Light from a stationary xenon arc lamp is split into red green and blue channel components and conducted to a translating optical system by multimode optical fiber cables. Each colour component is then modulated by a small-area PLZT light valve. An annular portion of the modulated light beam is reflected to a photodetector whose signal is used for closed-loop modulator control. The central transmitted portion of the modulated beam is combined with the other colour components into a single beam. This beam illuminates an aperture that is imaged onto the film. An overview of the mechanical electrical and optical concepts will be presented with emphasis on the optical design. 1.

Ahigh-resolution color film recorder was designed and developed that is capable of continuous tone color exposure of photographic positive and negative films in 8 in. x 10 in. single sheet formaL Exposure time for a full sheet is 10 minutes at a fixed resolution of 1000 pixels[mch. The film recorder employs small area light valves and a xenon arc light source along with the necessary optical and electrical components to provide the exposure control. The design of an exposure control system requires an understanding of the entire film recording system including ''well-defined'' performance requirements. A brief description of the film recorder will be given along with a more detailed discussion of the exposure control system design. The use of PLZT light valves in a continuous tone film writer presents many challenging electrical optical and mechanical problems. Special emphasis will be placed on the PLZT light valve geometry transfer characteristics (including nonlinearity hysteresis and drift) internal power dissipation and the associated control electronics needed to make this technology capable of meeting our performance requirements. 1.

Three high-resolution digital photographic printers based on different technologies have recently been designed and fabricated by the Photographic Research Laboratories of Easiman Kodak Company. All three printers were designed to produce continuous-tone pictorial color output of high quality using conventional photographic silver halide media (paper and film). Comparison of achieved spatial frequency response dynamic range colorimetric integrity and exposure energetics will be made for a CRTbased marking engine for printing on photographic paper a laserbased marking engine for printing on photographic paper or film and a PLZT light valve-based marking engine for exposing on film. Technological constraints inherent to the printers will be discussed and a comparison of price/performance attributes for the implementations will be made. 1. DEVICE DESCRIPTIONS 1. 1. CRT A high-resolution cathode ray tube is used as the exposure device in a digital printer breadboard capable of producing 3R (3. 5" x 5" ) and 4R (4" x 6" ) on roll photographic paper (Figure 1). The printer''s roll handling capability allows for a semi-automatic mode of operation with minimum operator intervention. Image resolution is 2000 pixels by 3000 lines over an active picture area of 4. 3" x 6. 4" resulting in a pixel pitch of 54 . t at the tube face. The spot profile of the 9" flat-face CRT used approximates a Gaussian shape with a measured diameter (FWHM) of 70 j. t at a

The Tektronix CFOT was used to expose Mead Cycolor and 3M dry silver photosensitive media. The results are presented and compared. The color gamut time to complete exposure and discernible resolution for the media are compared. Reciprocity failure and methods of minimizing the problems associated with it are discussed. The interactions between reciprocity failure and exposure time are discussed. The color coordinates attainable on the exposed media were determined by adjusting the paper feed speed and the intensity of the CFOT to obtain a range of exposures up to and beyond complete exposure. The CIELa*b* color coordinates of the media were measured with a Minolta color meter (Chroma Meter II). The discernible resolution was measured by exposing a 32 x 32 dot matrix on the media and then shrinking the dot to dot spacing between subsequent exposures to obtain a range of dot to dot spacings corresponding to resolutions ranging from 150 to 300 DPI. The exposed media was then examined under magnification to determine where uniform color fill was achieved. 1. CATHODE RAY TUBE DESCRIPTION The CFOT is a line scan tube with a fiber optic faceplate designed for producing full color hard copy on optically sensitive media. The tube has 3 stripes of phosphor each approximately . 060 inches wide by 8 inches long. The three phosphors are red green and blue enabling full color hard copy by sequentially

The printing of digitally generated images from medical diagnostic equipment has typically been done on analog systems after D to A conversion. Newer digital printing systems do not generally yield optimum results since they re-sample the incoming video signal according to their own internal pixel matrix. This leads to a loss of contrast and resolution plus the introduction of aliasing artifacts into the image. Using the method of synchronous sampling of the incoming video signal an almost perfect digitization of the original image can be achieved. Starting with the known display pixel matrix the pixel display clock can be regenerated by a precision phase locked frequency synthesizer. Quantizing levels are duplicated through calibration of the system. Sampling phase error is adjusted out such that each pixel is sampled at its center. Comparison with non-synchronous techniques and multi-generation performance of this system will be demonstrated. The images are then transferred digitally on disk for storage and later printing by a CRT based slow scan camera system. Image parameter files saved with the image allow the camera to generate a gamma correction look-up table for printing. The film image will then precisely and consistently match the CRT image viewed by the system operator. The system is capable of digitizing and printing up to 10242 images with the same high quality as the original displayed image.

This paper describes the implementation and performance of high speed light-emitting-diode (LED) printheads. The printhead is essentially a line of LED''s the width of a page and is used for printing on ordinary paper using the electro-photographic process. The printhead design approach adopted by Optotek uses a modular construction with 256 bits per module and a resolution of 300 DPI allowing construction of different sizes using a common building block. The unique design allows uniformity compensation through pulse width modulation of LED drive currents giving nearly equal energy outputs for all pixels. Since the intensity is measured after the printhead has been completely assembled the measurements incorporate variations in drivers LED''s and optics. the intensity measurements are used to burn on board compensation EPROMS providing 4 bits of uniformity compensation for each pixel. A common control for average intensity adjustment is included. Units of various lengths have been provided to a number of printer manufacturers in North America Europe and Japan. A 6144 element printhead is presently in production. This unit operates at a peak LED emission wavelength of 667nm and provides a pixel power of 2. 5 through self focusing fiber optics. A separate serial digital interface for each module allows an effective bitrate of 200 MHz for this unit. The modular design permits implementation of higher resolutions. LED emission wavelength can be tailored to match spectral sensitivity of photoreceptors.

Binary LED printbars in general have exposure non-uniformity associated with lens transmission nonuniformity LED brightness variations and electro-optical crosstalks (e. g. rise time degradation optical power starvation cross-talk noise as a function of LED pixels usage) that need to be corrected for a high quality printing system. We have designed a constant current Si driver array with two independent power supplies (logic and LED powers) coupled with an improved LED printhbar system to minimize the cross-talk artifacts. In order to improve on the average exposure uniformity of the LED printing system individual trimmable current source to each driver array is also provided. In addition to that a plural resolution printing method (400 x 2400) with a binary weighted correction scheme is used to reduce a binary printhbar''s printing non-uniformity of + or-iS to + or- 1. 0. 1.

The advantage of LED electrophotographic page printers is closely linked to the the process parameters of the printer. The electrical and mechanical processes and material properties were analyzed with respect to the affect on the print quality. Most critical to the print quality for the LED array printer is the constancy of the light intensity since the elements in the array are each independent light sources. It was found that the spot size can change significantly if the light intensity varies. Halftone printing uses the spot size to space size ratio to create the grayscale. The light intensity variation between elements can be 20 in non-compensated LED head arrays. If the need for light intensity compensation can be eliminated then a significant cost reduction in the LED head can be achieved. However the parameters of the basic electrophotographic processes must be carefully selected to assure a constant spot size and optimum print quality. The development method toner properties and the portion of the photoreceptor discharge curve used have the strongest influence on the spot size and halftone print quality. Transfer fusing and mechanical parameters have minimal effect. 1. LED PRINTING PROCESS The advantages of the LED printing process for high speed electrophotographic printers are well known. 1 Recently several printer manufacturers have introduced electrophotographic LED printers in the lower speed range. When compared to the scanning laser beam or liquid crystal

We have developed a Photo Addressed Liquid Crystal Light Valve (PALV) that incorporates Smectic C* liquid crystal and a photoconductor and a precise addressing method with laser scanning. The PALV system acts as a secondary imaging plate for imaging and printing. Fast writing speed of 2 sec and resolution of 10 lp/mm were achieved experimentally. The resolution mainly depends on driving frequency and alignment of Smectic C*. The PALV has the possibility of higher resolution in the future. 1.

A Bragg-angle holographic scanner (where both the incident beam and diffracted beam make equal angles with the spinner at mid scan) is described. Exact beam trajectory equations derived by vector analysis are presented for both a general holographic scanner and for the Bragg-angle scanner. Parametric data is presented for an example scanner and from this family of possible solutions conditions for minimum spinner diameter are determined. By adding output prisms between the spinner arid f-theta lens an additional significant reduction in spinner size is achieved. Other benefits of output prisms are described. 1.

During 1989 there were two major advances in the field of Japanese non-impact printing. The first was the technology which reduced the size and price of entry level laser printers. The introduction of the new low cost laser printers (with a street price of approximately $1 000) has a significant impact on the serial dot matrix, serial ink jet, and low end page printer market. One of the key technological breakthroughs was a new roller charging method that effectively eliminated corona discharge, and hence, removed the need for an ozone filter. The second was the electrophotographic color printing technology in which the image quality and connectivity to host systems were greatly improved. These advances along with the expanded thermal transfer product line have raised expectations for the general use of non-impact color printing in the office.